Security element and method for producing a security element

ABSTRACT

A method for producing a security element ( 55 ) and a security element ( 55 ) in the form of a multilayered film body having a top side facing the observer. The security element ( 55 ) has a volume hologram layer, in which a volume hologram is recorded, which provides a first optically variable information item. The security element ( 55 ) has a replication layer, in the surface of which a relief structure providing a second optically variable information item is molded and which is arranged above the volume hologram layer. A partial metallic layer is arranged between the volume hologram layer and the replication layer, wherein the metallic layer is provided in one or a plurality of first zones of the security element and the metallic layer is not provided in one or a plurality of second zones of the security element.

This application claims priority based on an International Applicationfiled under the Patent Cooperation Treaty, PCT/EP2009/002419, filed onApr. 2, 2009 and German Application No. DE 102008017652.4-45, filed onApr. 4, 2008.

BACKGROUND OF THE INVENTION

The invention relates to a security element in the form of amultilayered film body having a volume hologram layer, and to a methodfor producing such a security element.

Holograms are used as security elements for protecting securitydocuments such as banknotes, money substitutes, credit cards, passportsor ID documents and also for product protection. In mass-producedproducts, surface holograms are often used, by means of whichinteresting optically variable effects, for example movement effects,can be obtained and which are distinguished by a high luminousintensity.

Volume holograms, also referred to as white light holograms, in contrastto surface holograms, are based on diffraction of light at the Braggplanes of a transparent layer having local differences in refractiveindex.

A security element comprising a volume hologram and the production ofsuch a security element are described for example by DE 10 2006 016 139A1. In order to produce a multilayer body containing a volume hologram,a surface relief is used as master. The front side of the master isbrought into contact with the photosensitive layer of the multilayerbody directly or with interposition of a transparent optical medium, inwhich photosensitive layer the volume hologram is intended to berecorded. Afterward, the master is exposed with coherent light, aninterference pattern being formed by the superimposition of the lightradiated onto the master and the light diffracted by the master, whichinterference pattern is recorded in the photosensitive layer as a volumehologram. The volume hologram introduced into the photosensitive layerin this way is then fixed after the curing of the photosensitive layer.By means of a specific configuration of the master, two or more separateimage information items can be written into the photosensitive layer inthis case.

Further, EP 1 187 728 B1 describes the lamination of two volume hologramlayers one on top of the other, in which layers image information itemshave been written by means of different holographic recording methods.For the observer this gives rise to an overall impression composed ofthe image information items of the two volume hologram layers.

SUMMARY OF THE INVENTION

The invention is based on the object, then, of specifying an improvedsecurity element and a method for producing said security element.

The object of the invention is achieved by a security element in theform of a multilayered film body having a top side facing the observer,which security element has a volume hologram layer in which a volumehologram is recorded, which provides a first optically variableinformation item, which security element has a replication layer, in thesurface of which a relief structure providing a second opticallyvariable information item is molded and which is arranged above thevolume hologram layer, and wherein a partial metallic layer is arrangedbetween the volume hologram layer and the replication layer, wherein themetallic layer is provided in one or a plurality of first zones of thesecurity element and the metallic layer is not provided in one or aplurality of second zones of the security element. The object isfurthermore achieved by a method for producing a security element in theform of a multilayered film body having a top side facing the observer,wherein a multilayer body comprising a partial metallic layer and areplication layer is provided, wherein a relief structure providing asecond optically variable information item is molded in a surface of thereplication layer and the metallic layer is provided in one or aplurality of first zones of the security element and the metallic layeris not provided in one or a plurality of second zones of the securityelement, wherein a volume hologram layer is applied on that surface ofthe film body which lies closer to the metallic layer than to thereplication layer, such that the partial metallic layer is arrangedbetween the volume hologram layer and the replication layer, and in thatthe volume hologram layer is exposed with coherent light from that sideof the multilayer body which faces away from the volume hologram layer,through the partial metallic layer, for the purpose of recording avolume hologram in the volume hologram layer.

The invention provides a security element which can be counterfeitedonly with great difficulty and can nevertheless be manufactured in anexpedient manner. By virtue of the arrangement of the partial metalliclayer between the volume hologram layer and the replication layer, inwhich the relief structure is molded, on the one hand the optical effectof the domains of the volume hologram layer which lie below the metalliclayer in the first zones is suppressed, and on the other hand theoptical effect of the relief structure is caused to be manifested inthese zones. A seamless transition of the different optical effectsgenerated in the first and second zones is thus brought about, withoutthe volume hologram layer and the relief structure having to bepartially applied in a registered fashion with respect to one another.As a result, the first and second information items are generated in anundistorted manner and with high luminous intensity in domains lyingalongside one another with register accuracy, as a result of which abrilliant and impressive optically variable overall impression arisesfor the observer. Moreover, this impression cannot be imitated by anoptical copying method since the optically variable effect produced bythe volume hologram layer, on the one hand, and the optically variableeffect produced by the replication layer with the metallic layersituated beneath it, on the other hand, in each case cannot be imitatedby means of the respective other technology, and the structuresgenerating the first and the second optically variable information itemsthus mutually protect one another against counterfeiting. Furthermore,an intimate connection of the structures providing the first and secondinformation items is obtained by means of the sequence of the layers,such that the attempt to manipulate one structure automaticallyinfluences the optical impression of the other structure, such that anyattempt at manipulation is immediately recognizable. Moreover, in themethod according to the invention an intimate connection of the layersis obtained by virtue of the fact that the volume hologram is written inthe volume hologram layer through the partial metallic layer and thepartial metallic layer thus furthermore also produces the function of anexposure mask for writing the volume hologram. Thus, firstly, subsequentseparation of the layers is made more difficult and, secondly, such anattempt at manipulation is immediately recognizable since the volumehologram layer has domains in which no volume hologram is written intothe layer.

Further advantageous embodiments of the invention are presented in thedependent claims.

It is particularly advantageous for the relief structure to be moldedinto the underside of the replication layer and for the partial metalliclayer to be arranged directly between the replication layer and thevolume hologram layer. In the first zones, the first surface of themetallic layer thus adjoins the replication layer and the second surfaceof the metallic layer, lying opposite the first surface, adjoins thevolume hologram layer. In the second zones, the replication layerfurthermore adjoins the volume hologram layer.

The volume hologram layer thus directly adjoins the metallic layer inthe first zones and directly adjoins the replication layer in the secondzones, such that subsequent separation of the volume hologram layer ispossible only with difficulty on account of the adhesive bridges thusformed in the second zones. Moreover, a detachment attempt can berecognized, on account of the different adhesion behavior and adhesionforces in the first and second zones, directly from the resultantsurface pattern.

It is particularly advantageous in this case to choose the difference inrefractive index between the material of the replication layer and thematerial provided at the top side of the volume hologram layer, inparticular by selection of the material used for the replication layer,to be less than 0.2, preferably to choose the refractive index of thesematerials to be approximately identical. What is achieved thereby isthat, during the application of the volume hologram layer, the surfacestructures molded into the underside of the replication layer in thesecond zones are filled with a transparent material having a similarrefractive index, namely the material of the volume hologram layer, andthe optical effect of these structures is thus cancelled. This affordsthe advantage, firstly, that registration of the processes that mold therelief structure and the replication layer and of the processes thatstructure the metallic layer does not have to be effected. Furthermore,it is thus ensured that possible relief structures molded in thereplication layer in the domain of the second zones do not lead todistortions or corruptions of the recording result when the volumehologram is written into the volume hologram layer. It is thus possible,for example, for a surface relief to be molded into the replicationlayer over the whole area and for the optically variable informationthat arises for the observer only to be defined in a second step, forexample by the individualization of the metallic layer by means of alaser. Subsequent alteration of this information by subsequentprocessing of the metallic layer by means of a laser after the recordingof the volume hologram can be recognized directly in this case since, inthe case of the volume hologram written in accordance with the methodaccording to the invention, this volume hologram is present only incertain domains in the volume hologram layer and, consequently, such anattempt at manipulation can be recognized directly.

Depending on materials used for the replication layer and the volumehologram layer adjoining one another, it may be advantageous from caseto case to arrange an adhesion promoter layer between the replicationlayer and the volume hologram layer, the task of which adhesion promoterlayer is to intensify the adhesion of these two layers to one another orto establish adhesion between replication layer and adhesion promoterlayer and between volume hologram layer and adhesion promoter layerwhich is stronger than direct adhesion between the replication layer andthe volume hologram layer. In this case, the adhesion promoter layer hasa refractive index which differs by less than 0.2 from the refractiveindex of the material of the replication layer and the refractive indexof the material provided at the top side of the volume hologram layer.As a result, the adhesion promoter layer does not produce anydisturbing, in particular optical, effects during production or duringlater use of the security element.

Furthermore, it is also possible for an individualization of thesecurity element to be carried out by overprinting or by perforating aplurality of layers of the security element. Thus, it is possible, forexample, to apply on the top side of the security element, said top sidefacing the observer, an individualizing imprint that preferably extendsover a zone boundary between one or a plurality of first zones and oneor a plurality of second zones. In this case, it is particularlyadvantageous for the application of individualization information to becarried out by means of intaglio printing since, by this means, therelief structure molded in the replication layer and also the volumehologram layer are deformed by the pressure applied and are lastinglyaltered in terms of their optical properties. The introduction ofmicroperforations extending through at least the replication layer andthe volume hologram layer also leads to a lasting and irreversiblealteration of the layers that generate the optical effects. As a result,it is no longer possible to subsequently change the individualizedinformation for example by detachment or removal of an overprint andattempts at manipulation become immediately recognizable.

In accordance with one preferred embodiment of the invention, the one orthe plurality of first zones or the one or the plurality of second zonesare shaped in pattern form for the purpose of forming a thirdinformation item. Thus, by way of example, the first or the second zonesform pattern domains representing, for example, a portrait, a logo, aguilloche or an alphanumeric information item against a backgrounddomain formed by the second and/or first zones. In this case, it isparticularly advantageous to shape the first and/or second zones in theform of thin lines having a line width of <300 μm, preferably <150 μm,and, by means of such lines, to shape for example a guilloche or someother item of information recognizable to the human observer, forexample a portrait.

In accordance with a further preferred exemplary embodiment of theinvention, first and second zones are provided alternately in a firstdomain of the security element, and in this case first zones succeedingone another in at least one direction are spaced apart from one anotherby less than 300 μm. What is thereby achieved is that, in the firstdomain, the first and second optically variable information items appearto the human observer in one and the same domain and an opticallyvariable impression that is particularly succinct and very difficult tocounterfeit arises for the human observer in the first domain. It isthus possible to generate totally new color and movement effects for thehuman observer in the first domain as a security feature, which effectscan be provided neither by a volume hologram nor by a surface hologramas such.

Preferably, the ratio of the average width of the first zones to theratio of the average width of the second zones in the first domain isbetween 0.75:1 and 1:5. Thus, by way of example, preferably the width ofthe first zones is chosen to be less than 120 μm and the width of thesecond zones is chosen to be greater than 120 μm. Investigations haveshown that when the width of the first and second zones is chosen insuch a way, an optically variable impression that arises for the humanobserver in the first domain is particularly clear and of high luminousintensity.

Preferably, the first and second zones are arranged in accordance with aregular, one- or two-dimensional grid, for example a line grid or anarea grid. In this case, the form of the first and second zones can alsobe substructured further, for example have the form of alphanumericnumbers or of symbols, such that a further security feature that is onlyrecognizable by means of an aid is thereby provided. If an area grid ischosen, then the first zones and/or second zones are preferably shapedin punctiform fashion or in the form of a polygon. Furthermore, it isalso possible for the one- or two-dimensional grid to be a geometricallytransformed grid, for example a circularly or undulately transformedone-dimensional grid, such that, by way of example, the first zones areprovided in the form of concentric annuli or in the form of undulatinglines in the first domain.

In accordance with a further preferred embodiment of the invention, thefirst domain has a smallest dimension of more than 300 μm and is shapedin pattern form for the purpose of forming a fourth information item.The above-depicted superimposed optically variable impression thatarises in the first domain is thus provided for example in across-shaped domain or in a portrait-forming domain, as a result ofwhich further interesting and catchy optically variable effects can beobtained.

The relief structure molded in the replication layer is preferably arelief structure with dimensioning<50 μm, for example a diffractiongrating having a spatial frequency of 100 to 3500 lines/mm, a hologram,a zeroth-order diffraction structure, a blaze grating, a Kinoform, apreferably anisotropic matt structure or an isotropic matt structure, arefractive structure, for example a lens structure, for example amicrolens structure, a blaze grating or a prismatic structure, or acombination of one or more of the relief structures mentioned above.Furthermore, it is possible for the relief structure to be molded intothe replication layer over the whole area or merely into partial domainsof the replication layer, preferably to be molded into the replicationlayer only in the domain of the first zones.

The metallic layer preferably consists of aluminum, silver, gold,copper, chromium, SiO_(x), or of an alloy of these materials. The layerthickness of the metallic layer is preferably 0.1 to 100 nm, wherein thelayer thickness of the metallic layer is preferably chosen such that thedegree of opacity of the metallic layer is more than 40% to 50%,preferably more than 80%.

In accordance with one preferred exemplary embodiment of the invention,two or more information items from the group of first, second, third andfourth information items represent mutually complementary informationitems. Thus, by way of example, partial motifs of an overall motif arerespectively formed by the first and second optically variableinformation items. By way of example, the second information item formsleaves of a tree represented by the first information item. As a result,what is furthermore achieved is that any manipulation of one of thelayers of the security element, even a very slight manipulation,immediately becomes intuitively recognizable to the human observer.

Furthermore, it is also possible for first, second, third and fourthinformation items to be provided in a manner lying alongside one anotheror overlying one another in the security element. Thus, it is possible,for example, to shape first zones in the form of an image, for exampleof a flower pattern, in a first domain (third information item), toarrange first and second zones in accordance with a grid in a seconddomain in pattern form (fourth information item) and to shape the firstzones in the form of a thin line, producing a pictorial representation,preferably having a line width of less than 120 μm, in a third domain.These domains can also overlie one another in part. Furthermore, it isalso possible to provide first zones having a line width of less than 50μm in further domains, for example to shape the first zones in the formof a microtext.

In accordance with one preferred exemplary embodiment of the invention,the volume hologram master is arranged below the volume hologram layerin direct contact with the volume hologram layer or in a mannerseparated from the volume hologram layer by an optical medium. In thiscase, the volume hologram master used is preferably a volume hologrammaster which has an optically variable surface relief and which isprovided with a reflection layer. It is also possible, however, to useinstead of a surface relief as volume hologram master also a volumehologram, as is the case in traditional recording technology for volumeholograms wherein a volume hologram master is used for recording avolume hologram. A combination of a surface relief master and a volumehologram master can also be used during the recording of the volumehologram. Furthermore, it is also possible for the volume hologrammaster to be arranged on the side facing away from the volume hologramlayer and for the coherent light used for the recording of the volumehologram to pass through a volume hologram master arranged in this wayor to be reflected by a volume hologram master arranged in this waybefore it passes through the replication layer and the partial metallayer in order to expose the volume hologram layer. In this case thereference beam is preferably radiated in from the opposite side, that isto say from the side facing the volume hologram layer, onto the volumehologram layer for the purpose of forming the interference pattern.

The color of the volume hologram recorded in the volume hologram layeris preferably determined by the wavelength of the light used for theexposure, by the angle of incidence of the light used for the exposure,by the diffraction behavior of the volume hologram master, in particularby the latter's surface relief, grating period or azimuth angle, and bythe photopolymer, the curing process for the photopolymer, and anoptional treatment of the photopolymer for shrinkage or swelling of thevolume hologram layer.

For the purpose of producing multicolor volume holograms it is thuspossible, for example, to shrink or to swell the volume hologram layerin certain domains by means of different curing processes or differentaftertreatments in certain domains, and thus to generate domains inwhich the volume hologram of the volume hologram layer exhibits adifferent color.

In accordance with one preferred embodiment of the invention, thefollowing method is carried out for producing multicolor volumeholograms:

Two or more lasers are used for the exposure of the volume hologramlayer. In this case, it is possible, firstly, for the volume hologramlayer to be exposed by the light beams generated by the respectivelasers at a different angle of incidence, such that each of the lasersgenerates an image domain of the volume hologram which has a differentcolor value. Furthermore, it is also possible for the lasers to emitlight having different wavelengths and thus for image domains havingdifferent color values to be recorded in the volume hologram layer bymeans of the respective lasers. In this case, it is particularlyadvantageous if the light generated by the two or more lasers is coupledby means of a coupler in a light beam used for recording the volumehologram in the volume hologram layer. The methods described above canalso be combined with one another.

For the purpose of generating a multicolor volume hologram with imagedomains having different color values, the procedure adopted in thiscase is preferably as follows:

The lasers, a modulator arranged in the beam path between the respectivelaser and the volume hologram layer and/or a deflection elementdetermining the angle of incidence of the exposure beams arecorrespondingly driven such that the respective image domain that is tohave a predefined color value is exposed with a light having an exposurewavelength and/or light which impinges at an angle and which bringsabout recording of a volume hologram image domain with the predefinedcolor value. Furthermore, it is also possible in this case to arrangeexposure masks in the beam path between the two or more lasers and thevolume hologram layer, which determine the position and shaping of theimage domains recorded by the respective laser.

Preferably, in this case, the two or more lasers, the modulators and/orthe deflection elements are driven in this case by a control unit, whichdetermines the position of the volume hologram master with respect tothe lasers by means of a position sensor, for example, and controls aregister-accurate exposure of the volume hologram master by means of thetwo or more lasers for the purpose of generating the multicolor volumehologram. Consequently, it is possible for different domains of thevolume hologram master, which can each have different diffractivestructures (for example with differences in terms of the structureprofile, azimuth or line spacing), to be exposed with laser light havingdifferent parameters (e.g. angle of incidence, wavelength orpolarization).

The object of the invention is furthermore achieved by a securityelement in the form of a multilayered film body having a top side facingthe observer and having a volume hologram, wherein the security elementhas a replication layer, in the surface of which a relief structure ismolded, which has one or a plurality of first regions having a reliefdepth of the relief structure of more than 10 μm, preferably more than15 μm, and has one or a plurality of second regions having a reliefdepth of the relief structure of less than 2 μm, in particular less than1 μm, and wherein the first regions of the replication layer are filledwith a volume hologram material, in which the volume hologram isrecorded, which provides a first optically variable information item.The object is furthermore achieved by a method for producing a securityelement in the form of a multilayered film body having a top side facingthe observer, wherein a multilayer body comprising a replication layeris provided, in the surface of which a relief structure is molded, whichhas one or a plurality of first regions having a relief depth of therelief structure of more than 10 μm and one or a plurality of secondregions having a relief depth of the relief structure of less than 2 μm,in particular less than 1 μm, wherein the first regions of thereplication layer are filled with a volume hologram material, and thevolume hologram material is exposed in the first regions for the purposeof recording a volume hologram.

The recording of the volume hologram is effected by means of a volumehologram master. Afterward, the volume hologram material is cured andthe volume hologram is thus fixed. With regard to these process steps,reference is made to the above explanations, which are correspondinglyapplicable to this exemplary embodiment, too, and can preferably becorrespondingly combined with this exemplary embodiment.

The procedure described above makes it possible to influence the opticalappearance of a volume hologram such that the latter cannot be imitatedby an optical copying method and a security element which can becounterfeited only with difficulty and which is distinguished by noveloptically variable effects is thus provided. By virtue of the fact that,in the first regions, the relief structure with a relief depth of morethan 10 μm, preferably of more than 15 μm, is molded into thereplication lacquer layer, a distinctly different optical impression inthe first and second regions arises even when the volume hologrammaterial is applied over the whole area both in the first and in thesecond regions and when a volume hologram is subsequently recorded intothe volume hologram layer. In particular, what is brought about withsuitable selection of the application weight of the volume hologrammaterial (even in the case of whole-area application) is that the volumehologram, after exposure and curing, is generated only in the firstregions, but not in the second regions. This can be used, for example,for additionally modulating the brightness of the volume hologram as itappears to the observer, and thus for introducing additional grey-scaleinformation into the optically variable appearance manifested to theobserver. Furthermore, it is also possible, however, for opticallyvariable effects which are generated by a volume hologram and opticallyvariable effects which are brought about by a surface relief structurethereby to be realized in an aligned manner with register accuracy withrespect to one another in a security element.

In this case, the relief depth of the relief structure should beunderstood to mean the difference between the layer thickness of thereplication layer at its thickest location and the layer thickness ofthe replication layer at the local location respectively underconsideration.

Preferably, the layer thickness with which the volume hologram materialis provided in the first regions differs from the layer thickness withwhich the volume hologram material is provided in the second regions byat least 8 μm, with further preference by at least 15 μm. The layerthickness of the volume hologram material in the second domains ispreferably less than 5 μm, and the layer thickness of the volumehologram material in the first domains is more than 10 μm, preferablymore than 15 μm.

The replication layer can in this case also consist of a carrier film orcomprise a plurality of layers.

In accordance with one preferred exemplary embodiment of the invention,a liquid volume hologram material is applied to the multilayer bodycomprising the replication layer, for example by being poured on,sprayed on or printed on.

In this case, the volume hologram material is preferably applied inpreferably liquid form, that is to say with a dynamic viscosity ofbetween approximately 0.001 N*s/m² and approximately 50 N*s/m².Preference is given to a low-viscosity volume hologram material having alow viscosity of, for example, approximately 0.001 N*s/m², whichcorresponds to an approximately aqueous consistency, which fills therelief structure well.

Preferably, the volume hologram material applied in liquid form is wipedaway by means of a doctor blade, such that the volume hologram materialcompletely fills the relief structure in the first regions and thevolume hologram material is not present, or is present only with a smalllayer thickness, preferably with a layer thickness of less than 5 μm, inthe second regions. The use of a doctor blade can also be dispensed withif the volume hologram material is applied to the multilayer body withcorrespondingly low viscosity and the application weight is chosen suchthat the layer thickness of the volume hologram layer in the firstregions and that in the second regions differ by at least 10 μm.However, the volume hologram material can also have a high viscosity,that is to say be present for example with honey-like or paste-likeviscosity, which then necessitates processing by means of a doctorblade, such that the volume hologram material completely fills therelief structure in the first regions and the volume hologram materialis not present, or is present only with a small layer thickness,preferably with a layer thickness of less than 5 μm, in the secondregions.

In accordance with one preferred exemplary embodiment of the invention,the relief structure has, in the second regions or in partial regions ofthe second regions, structure elements providing a second opticallyvariable information item. The relief structure thus has a finestructure having a relief depth of less than 1 μm in the second regionsor in partial regions of the second regions and valleys of a coarsestructure having a relief depth of more than 10 μm in the first regions,wherein the fine structures determine the information content of thesecond optically variable information item and the coarse structuresdefine the domains in which ultimately the volume hologram manifests anoptical effect. Since the fine structures and the coarse structures aremolded in a single replication step, the domains in which the first andsecond optically variable information items can be generated arearranged with absolute register accuracy with respect to one another,that is to say practically without deviation from the arrangement orpositioning of the domains relative to one another on the common volumehologram master. Furthermore, an intimate connection of the structuresthat provide the first and second information items is obtained thereby,such that, as already described above, the attempt to manipulate onestructure automatically influences the optical impression of the otherstructure and, consequently, any attempt at manipulation is immediatelyrecognizable.

The structure elements provided in the second regions or the partialregions of the second regions preferably form a diffractive structure,for example a hologram or a Kinegram®, a matt structure, a linear orcrossed diffraction grating, isotropic or anisotropic matt structures,blaze gratings, zeroth-order diffraction gratings, or combinations ofsuch diffractive structures, or a refractive structure, or amacrostructure, and are preferably formed in the manner described above.Preferably, the second regions or partial regions of the second regionsare furthermore provided with a reflection layer, in particular anopaque metallic layer, such that, for example, the security element hasa metallic layer which is provided in the second regions or in partialregions of the second regions and is not provided in the first regions.The metallic layer in the second regions can be provided either over thewhole area there or partially. The metallic layer can also be providedas a regular or irregular, partial or whole-area grid. Preferably, themetallic layer is arranged partially and with register accuracy withrespect to the design of the diffractive structures in the secondregions.

Instead of the metallic layer, a nonmetallic reflection layer can alsobe provided, e.g. an opaque lacquer having preferably a high differencein refractive index with respect to the material of the structureelements. A nonmetallic, transparent reflection layer composed of an HRImaterial having a high refractive index (HRI), can also be provided.

With appropriate selection of the optical refractive indices of thereplication layer and of the volume hologram material (difference inrefractive index greater than approximately 0.2, preferably greater than0.5) and/or with appropriate application of a (whole-area) reflectionlayer to the multilayer body after application of the volume hologrammaterial, said reflection layer can also be dispensed with.

In this case, it has proved to be particularly advantageous to apply areflection layer by means of the method described below in the secondregions of the replication layer:

It is thus possible, for example, to provide the surface of themultilayer body having the relief structure with a thin metal layerbefore the application of the volume hologram material and then toutilize the different relief depth of the relief structure in the firstand second regions for the register-accurate demetallization of saidmetal layer in the first regions. It is thus possible, for example, toapply an etching resist by printing, in which case the inking by meansof the printing roller takes place only on the elevated second regions,but not on the distinctly recessed first regions. Afterward, the metallayer is removed in the domains not covered with the etching resistlayer, that is to say the recessed first regions, in an etching process.Furthermore, it is also possible for an etchant to be introduced bydoctor blade into the depression, that is to say into the first zone,and to bring about the removal of the metal layer there.

In accordance with one preferred exemplary embodiment of the invention,the area proportion constituted by the first regions in the area of atleast one first domain of the security element differs from the areaproportion constituted by the first regions in the area of at least onesecond domain of the security element. This has the effect that theluminous intensity of the volume hologram differs in the first domainand in the second domain. Through appropriate choice of the areaproportions constituted by the first region, it is thus possible to setthe brightness of pixels of the volume hologram and to modulateadditional “grey-scale information” onto the volume hologram.

Preferably, the first regions for this purpose have a smallest dimensionof less than 400 μm preferably of less than 200 μm. This has the effectthat the splitting into first and second regions can no longer beresolved by the human observer and a continuous image impression thusarises. The smallest dimensions of the first regions preferably have asmallest dimension of more than 20 μm in order to ensure reliablefilling of the first regions with the volume hologram material.

Furthermore, it is possible to bring about the brightness value of thevolume hologram by varying the distance between the first regions and/orby varying the area occupied by the respective first region. It ispossible to arrange the first regions in a one- or two-dimensional gridand to choose the grid width and/or the area occupied by the respectivefirst regions to be correspondingly different in the first/seconddomains. The first and second regions can be configured in accordancewith the first and second zones described above.

Furthermore, it is also possible for the partial regions of the secondregions or the second regions to be shaped and formed in accordance withthe first zones described above, and for the domains which are assignedto the second zones described above to have first and second regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example below on the basis of aplurality of exemplary embodiments with the aid of the accompanyingdrawings.

FIG. 1 a to FIG. 1 c show in each case a schematic illustration of amethod sequence in accordance with the method according to the inventionfor producing a security element.

FIG. 2 shows a schematic sectional illustration of a film body providedfor carrying out the methods according to FIG. 1 a to FIG. 1 c.

FIG. 3 shows a schematic sectional illustration of a multilayer bodywhich occurs as an intermediate product in the methods according to FIG.1 a to FIG. 1 c.

FIG. 4 shows a schematic sectional illustration of a multilayer bodythat forms an intermediate product in a further exemplary embodiment ofthe invention.

FIG. 5 shows a schematic sectional illustration of a multilayer bodywhich occurs as an intermediate product in the methods according to FIG.1 a to FIG. 1 c.

FIG. 6 shows a schematic sectional illustration of a multilayer bodywhich occurs as an intermediate product in the methods according to FIG.1 a to FIG. 1 c.

FIG. 7 shows a schematic sectional illustration of a multilayered filmbody.

FIG. 8 shows a schematic, enlarged plan view of the security elementaccording to FIG. 7.

FIG. 9 a and FIG. 9 b show schematic sectional illustrations of a filmbody for a further exemplary embodiment of the invention.

FIG. 10 a to FIG. 10 c show schematic sectional illustrations of a filmbody for a further exemplary embodiment of the invention.

FIG. 10 d shows an illustration of an optical information item providedby a film body according to the invention.

FIG. 11 a and FIG. 11 b show schematic sectional illustrations of a filmbody for a further exemplary embodiment of the invention.

FIG. 12 a shows an illustration of an optical information item providedby a film body according to the invention.

FIG. 12 b shows a schematic plan view of a volume hologram master.

FIG. 12 c shows a schematic plan view of a volume hologram master with aplurality of exposure domains.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 a illustrates the procedure when producing a security elementaccording to the invention. FIG. 1 a shows a coating station 38, anexposure station 40, an exposure station 47 and a coating station 39. Afilm body 51 is fed to the coating station 38. A volume hologram layeris applied on the film body 51 by the coating station 38, for example bya surface of the film body 51 being coated over the whole area orpartially with a photopolymer material 37, which forms the volumehologram layer, by printing, spraying or pouring. The resultantmultilayer body 52 is subsequently fed to the exposure station 40,where, for the purpose of recording a volume hologram into the volumehologram layer, it is exposed with coherent light 45 from the laser 44and subsequently irradiated by the UV light source 46. The resultantmultilayer body 53 is fed to the exposure station 47 in order to achievecomplete curing of the volume hologram layer. The resultant multilayerbody 54 is fed to the coating station 39, by which one or a plurality offurther layers are applied to the multilayer body 54. Thus, by way ofexample, an adhesive layer is applied to a surface of the multilayerbody 54 over the whole area by the coating station 39, thus resulting inthe multilayer body 55.

The detailed sequence of the method illustrated in FIG. 1 a is explainedbelow with reference to the following figures:

FIG. 2 shows the multilayer body 51. The multilayer body 51 has atransparent carrier film 10 and a replication layer 11. The carrier film10 is a preferably biaxially oriented plastic film having a layerthickness of between 15 and 100 μm, preferably between 16 and 30 μm. Byway of example, the carrier film is a PET, PEN or BOPP film.

The replication layer 11 is preferably applied to the carrier film 10 ina layer thickness of 0.1 to 25 μm, preferably approximately 20 μm. Thereplication layer 11 consists of a thermoplastic, that is to saythermally curable and/or thermally dryable, or UV-curable replicationlacquer or of a replication lacquer comprising thermoplastic andUV-curable components. As an alternative thereto, the carrier filmitself 10 can also serve as a replication layer, that is to say that therelief structure 20 can be molded directly in the carrier film 10. Aseparate replication layer composed of replication lacquer is then nolonger necessary, as a result of which the thickness of the securityelement can be reduced. Furthermore, it is also possible for thereplication layer to consist of the carrier film 10 and a replicationlacquer layer, wherein, depending on the relief depth, the reliefstructure extends into the replication layer or into the carrier layer,that is to say that the replication lacquer layer is through-embossed inthe domain of the deep structures. A relief structure 20 is molded intothe underside of the replication layer 11 over the whole area. Forexample by means of a heated embossing tool by which the reliefstructure 20 is molded by means of heat and pressure into thereplication layer 11 formed by a thermoplastic replication lacquer.Furthermore, it is also possible for the relief structure 20 to bemolded into the underside of the replication layer 11 by means of UVreplication, by a procedure in which the replication layer 11, after themolding of the surface relief by means of a correspondingly shapedcountermold, is irradiated with UV light and cured. Furthermore, it isalso possible for the relief structure 20 to be introduced into thesurface of the replication layer 11 by means of a laser or some otherablative method.

The relief structure 20 is a diffractive, optically variable surfacestructure, for example a hologram, a preferably sinusoidal diffractiongrating, an asymmetrical relief structure, a blaze grating, a preferablyanisotropic or isotropic, holographically produced matt structure, aKinegram®, a computer generated hologram, or a combination of such finerelief structures having a diffraction-optical effect, the structuresizes of which are approximately in the size range of the wavelengths ofvisible light, that is to say approximately in the range of below 1000nm.

Preferably, the distance between adjacent local maxima is in this caseless than 50 μm, such that higher diffraction orders are suppressed anda distinctly perceptible optically variable impression is provided bythe relief structure 20. Furthermore, it is also possible for the reliefstructure to be formed by a zeroth-order diffraction grating, whereinthe distances between adjacent structure elements are in the range of orless than the wavelength of light visible to the human observer.Furthermore, it is also possible for the relief structure 20 to beformed by macroscopic structures having a refractive effect, for examplemicroprisms or lens-type structures or binary, rectangular structures,the local distance between which can be in the range of up to a few mm,preferably up to 500 μm. Preferably, the structure dimensions are lessthan 40 μm. The relief structure 20 can also be formed by a combination,for example area domains arranged alongside one another, composed ofmacroscopic structures having a refractive effect and microscopicstructures having a diffractive effect, or composed of a superimpositionof macroscopic structures having a refractive effect with microscopicstructures having a diffractive effect. Diffractive and refractivestructures can be molded in the replication layer 11 simultaneously bymeans of one and the same embossing tool, such that an exactlyregister-accurate arrangement of both structures with respect to oneanother can be effected. Thus, diffractive and refractive structures canbe present alongside one another in separate domains or else in commondomains, for example in a manner interlaced in one another.

In this case, the distance between the local maxima of the reliefstructure 20 or the local periodicity of the relief structure 20 ischosen independently of the periodicity of a grid formed by first andsecond domains and of the width of the first or second domains.

A partial metallic layer 13 is furthermore applied to the replicationlayer 11, wherein the metallic layer 13 is provided in first zones 31 ofthe multilayer body 51 and is not provided in second zones 32 of themultilayer body 51, as is illustrated by way of example in FIG. 2. Themetallic layer 13 preferably consists of aluminum, copper, gold, silver,chromium or SiO_(x) or an alloy of these materials and preferably has athickness of 0.1 to 100 nm.

In order to produce the partial metallic layer 13, in this case theunderside of the replication layer 11 is coated with a metallic layerpreferably over the whole area and when the metallic layer issubsequently removed again in the zones 32, for example bypositive/negative etching or by means of ablation. In this case, it ispossible, in particular, to remove the metallic layer by means of alaser in the zones 32, in order thus to obtain an individualization ofthe security element to be produced. Furthermore, it is also possiblefor the metallic layer to be applied to the replication layer 11 only incertain domains and, under certain circumstances, already in patternform, for example by means of vapor deposition masks. A combination ofthe above-described demetallization and ablation methods is alsopossible in order, for example, to introduce an individualizableinformation item, for example a consecutive number, only into a partialdomain.

Furthermore, it is also possible for the multilayer body 51 additionallyto have one or a plurality of further layers alongside the layers shownin FIG. 2. It is thus possible, for example, for the multilayer body 51additionally to have one or a plurality of further layers between thecarrier layer 10 and the replication layer 11 in order, for example, tomake available a transfer film, for example a hot embossing film, as endproduct. In this case, the film body 51 preferably additionally has arelease layer and a protective lacquer layer, which are provided betweenthe carrier layer 10 and the replication layer 11. Furthermore, it isalso possible for the multilayer body 51 additionally to have one or aplurality of further decorative layers, for example additionally to haveone or a plurality of colored lacquer layers.

A polymer that forms a volume hologram layer is then applied on theunderside of the multilayer body 51 in a first step. This is effected bymeans of a printing method, for example, preferably by means of smearingmethods. In this case, the photopolymer is applied to the underside ofthe multilayer body 51 preferably in a layer thickness of 5 to 100 μm,with further preference in a layer thickness of approximately 20 μm.This gives rise to the multilayer body 52 shown in FIG. 3, saidmultilayer body furthermore having a volume hologram layer 12 alongsidethe layers 10, 11 and 13 already explained with reference to FIG. 2.

In the case of a volume hologram layer 12 that is to be produced onlypartially, the film body 51 can have a macroscopic and/or microscopicsurface profile preferably having a depth of approximately 10 to 50 μm,particularly preferably approximately 15 to 20 μm. After the preferablywhole-area application of the photopolymer material 37 by printing,spraying or pouring, the photopolymer material 37, by means of a doctorblade, for example, is pressed to an even greater extent into the deepstructures and is at least substantially removed from the surface of thefilm body 51 outside the depressions, thus giving rise to surfaceregions on the film body 51 which are covered with photopolymer material37 and adjoining surface regions which are to the greatest possibleextent free of, or not covered by, photopolymer material 37. This willbe explained further below in detail with reference to FIGS. 9 a to 11b.

The photopolymer used for the volume hologram layer 12 is, for example,the photopolymer Omni DEX 706 from Dupont. Furthermore, it is alsopossible to use photopolymers which are present as a liquid substanceand are polymerized and thereby cured for example by the action of UVlight. Provision can also be made for applying the photopolymer as alayer by pouring and precuring it by means of weak UV light action orthermal treatment.

Preferably, in this case the material used for the replication layer 11is chosen such that the refractive index of the material of thereplication layer 11 and the refractive index of the as yet unexposedvolume hologram layer are approximately identical or have a differencein refractive index of less than 0.2. This ensures that, during thesubsequent exposure, the domains of the surface structure 20 which arestill present in the zones 32—as indicated in FIG. 3—are filled with amaterial having approximately the same refractive index and thus cannotcorrupt the recording of the volume hologram in the volume hologramlayer 12.

Thus, the following layer is used as replication layer 11, for example:

Replication layer 11 Methyl ethyl ketone 2100 g Toluene 750 gCyclohexanone 1000 g Acetyl tributyl citrate 30 g Nitrocellulose(ester-soluble, standard 34 E) 1000 g Methyl methacrylate-butyl acrylatecopolymer 180 g (T_(glass) 80° C., T_(soften) ca. 120° C.) T_(glass) =glass transition temperature; T_(soften) = softening temperature

Furthermore, it is also possible to provide, in addition to the layer13, an HRI (high refractive index) layer having a high refractive index,for example consisting of ZnS, which covers the surface structure 20preferably over the whole area. This additional layer can be applied tothe film body before or after the shaping of the layer 13.

FIG. 4 shows a multilayer body 61, likewise having a carrier layer 10, areplication layer 11 and a volume hologram layer 12, which are formed inthe manner explained above with reference to FIG. 2 and FIG. 3. Incontrast to the multilayer body 52, in the case of the multilayer body61, a relief structure 21 molded into the replication layer 11 only inthe zones 31, rather than over the whole area, is molded into thereplication layer 11. Furthermore, is also possible for the domains inwhich the relief structure 21 is molded into the replication layer 11and the zones 31 in which the metallic layer 13 is provided to bedesigned with regard to their dimensions such that, in the case of theregister deviations that occur in registration methods used in theproduction process between the demetallization process and thereplication process, it is ensured that the relief structure 21 ismolded in the zones 31. For example by the dimensioning of the domainsprovided with the relief structure 21 being enlarged relative to thezones 31 by the register deviation or by double the register deviation.Furthermore, it is also possible for the zones 31 to be provided withthe relief structure 21 only in certain domains, and, for example, forthe domains in which the relief structure 21 is provided to be chosen inpattern form independently of the shaping of the zones 31.

The multilayer body 52 described in FIG. 3 is then fed to the exposurestation 40. The exposure station 40 has a volume hologram master 41attached to the surface of an exposure roller. In this case, theunderside of the multilayer body 52 bears on the surface of the exposureroller, thus resulting in the arrangement shown in FIG. 5: the volumehologram master 41 with surface structures 43 and 42 is in directcontact with the still soft material of the volume hologram layer 12.Furthermore, it is also possible here to provide a transparent spacerlayer between the volume hologram master and the multilayer body 52 inorder thus to improve the service life of the master, for example.

Furthermore, is also possible for the volume hologram master used not tobe a master provided with a surface relief, but rather a volumehologram, and for the recording of the volume hologram in the volumehologram layer to be effected by means of a customary holographiccopying method for forming a transmission or reflection hologram in thevolume hologram layer.

Furthermore, it is also possible for the volume hologram master not tobe attached on an exposure roller, as shown in FIG. 3, and for theexposure not to be effected in a continuous roll-to-roll process, butrather for the exposure to be effected section by section in a“step-and-repeat” process.

The structures described in DE 10 2006 016 139, for example, can be usedas relief structure 42 and 43, wherein the structures 43 are moth eyestructures, for example. With regard to the details of the exposuremethod, reference is likewise made to said document.

If the volume hologram layer is then irradiated by means of a laser 44with coherent light 45 for the purpose of writing the volume hologrampredetermined by the structures 42 and 43 into the volume hologram layer12, then the effect shown in FIG. 6 arises: the incident light 45 isreflected by the metallic layer 13 in the zones 31 and does notpenetrate into the underlying volume hologram layer 12. Preferably, thecoherent light 45 is in this case radiated in at an angle of incidenceof approximately 15 degrees with respect to the normal to the top sideof the multilayer body 52. In the zones 32, the light 45 penetratesthrough the volume hologram layer 12 and is diffracted back by theunderlying surface relief of the volume hologram master 41, as a resultof which, in the zones 32, an interference pattern forms from thesuperimposition of the incident and diffracted-back light rays in thevolume hologram layer 12. This interference pattern is then recorded inthe volume hologram layer 12.

The volume hologram is therefore written into the volume hologram layer12 in the zones 32 and only in the edge domains of the zones 31. Thewriting of the volume hologram into the core domain of the zones 31 isprevented by the partial metallic layer 13.

In this case, it is possible to use two or more lasers, preferablyoperating in a scanning fashion, the emitted coherent light from whichis incident at different angles of incidence in the volume hologramlayer 12. This is shown by way of example in FIGS. 1 b and 1 c. In thiscase, the angles of incidence of the lasers can lie in a plane which isarranged approximately perpendicular to the cylinder axis of thecylindrical volume hologram master 41 in FIGS. 1 b and 1 c, or else liein a plane which is arranged approximately parallel to the cylinder axisof the cylindrical volume hologram master 41 in FIGS. 1 b and 1 c.

FIG. 1 b illustrates a method in which two lasers are used, which arearranged such that the coherent light emitted by them is incident atdifferent angles of incidence in the volume hologram layer 12. Themethod according to FIG. 1 b thus corresponds to the method according toFIG. 1 a with the difference that two lasers 44 a and 44 b are providedinstead of the laser 44, wherein the coherent light 45 a and 45 brespectively generated by said lasers 44 a and 44 b is incident atdifferent angles on the volume hologram layer 12. Furthermore, arespective modulator 441 and 442 is arranged in the beam path betweenthe lasers 44 a and 44 b and the volume hologram layer 12 in order tocontrol the coherent light 45 a and 45 b, respectively, which isincident on the volume hologram layer 12, as is explained in greaterdetail further below. In this case, the modulator 441 and/or 442 is anoptional element. Without modulator 441 and/or 442, the laser can exposethe volume hologram layer 12 over the whole area or the laser ismodified with the aid of masks (not illustrated in more specific detail)or else regulated laser-internally.

The lasers 44 a and 44 b can emit coherent light 45 a, and 45 b,respectively, having identical or different wavelengths. As a result, amulticolored image can arise in the volume hologram layer 12 because thelaser beam impinges on the photopolymer at a respectively differentangle or passes through said photopolymer at a respectively differentangle and thereby produces differently extending Bragg planes that areresponsible for the optical image. Depending on the variation of theangle of incidence and/or of the laser light wavelengths, differentcolors of the optical image or of the optically perceptible effect areproduced.

Proceeding from a predefined arrangement of photopolymer material andvolume hologram master with predefined structures and coherent lighthaving a predefined color/wavelength, a variation in the wavelength ofthe light color of the optically perceptible effect arises uponvariation of the angle of incidence of the coherent light with respectto the normal to the top side of the multilayer body 52. If the angle ofincidence is increased, for example, that is to say if the coherentlight is radiated with flatter incidence with respect to the top side ofthe multilayer body 52, the wavelength of the light color of theoptically perceptible effect shifts into the longer-wave range becausethe path of the beam in the material layer of the photopolymer becomeslonger in the case of flatter incidence. By way of example, ayellowish-green light color (with a longer wavelength than green) of theoptically perceptible effect can be obtained by increasing the angle ofincidence of green coherent light or a bluish-green (with a shorterwavelength than green) light color of the optically perceptible effectcan be obtained by decreasing the angle of incidence of green coherentlight.

With a predefined volume hologram master and a plurality of lasers withdifferently colored coherent light, by means of the variation of theangle of incidence of the coherent light it is also possible toinfluence whether or not the optically perceptible effect is dependenton viewing angle. If differently colored coherent light is radiated inat approximately identical angles of incidence, a multicolored opticallyperceptible effect arises which, however, is dependent on viewing angleand exhibits only one of the resulting colors in each case, depending onthe viewing angle. If all of the generated colors are intended to bevisible simultaneously, that is to say at one and the same viewingangle, the angle of incidence of the individual colors of the coherentlight has to be varied accordingly, in which case it holds true that thehigher the wavelength of the incident coherent light, the lower therequired angle of incidence relative to the normal to the top side ofthe multilayer body 52. Also conceivable in this case is an angle ofincidence of approximately 0 degrees in the case of long-wave red light,e.g. approximately 15 degrees in the case of green light (mediumwavelength range of the visible spectrum) and approximately 30 degreesin the case of short-wave blue light. The perceptible optical effectcomposed of red, green and blue portions would then be visible at acommon viewing angle or else at a common viewing angle range.

As an alternative thereto, it is possible to use two or more lasers,preferably operating in a scanning fashion, which emit coherent lighthaving different wavelengths and the beams of which are coupled to oneanother by means of a coupler based on polarization or reflection (e.g.two prisms adhesively bonded together at their bases) such that thecoupled beams of all the lasers are incident at a common angle ofincidence in the volume hologram layer 12.

A method in which the volume hologram layer 12 is exposed by means of anexposure arrangement arranged in this way is shown by way of example inFIG. 1 c. The method in accordance with FIG. 1 c corresponds to that inaccordance with FIG. 1 a with the difference that, instead of theexposure by the laser 44, the exposure of the volume hologram layer 12is effected by an exposure arrangement consisting of two lasers 44 a and44 c, two modulators 443 and 444 and a coupler 445. The lasers 44 a and44 c generate coherent light having different wavelengths which iscoupled by means of the coupler 445 and radiated as light 45 onto thevolume hologram layer 12. The exposure of the volume hologram layer 12by means of the two lasers 44 a and 44 c can be controlled simply andrapidly via a driving of the coupler 445.

In order to form an image with this coupled or combined light beam, itis advantageous if the light beam intensity is modulated, for example byindividual partial beams being switched on and off (binary modulation).Specific lasers (e.g. diode lasers) can be modulated directly. Otherlasers can be modulated at a sufficiently high speed by means ofexternal modulators, for example the modulators 443 and 444, e.g. bymeans of acousto-optical or electro-optical modulators. It is alsopossible to produce a modulation by means of a shutter or chopper or tomodulate the laser beams individually or jointly by means of masks ordiaphragms.

Preferably, the arrangements according to FIG. 1 b and FIG. 1 c have asensor element and a control unit. The sensor element detects theposition of the volume hologram master. For this purpose, it eithersenses the surface of the cylinder 41 optically or detects the angularposition of the cylinder 41 by means of a rotary encoder. The controlunit uses the position of the volume hologram master determined directlyor indirectly by the sensor element as an input parameter for drivingthe lasers 44 a, 44 b, 44 c and/or the modulators 441 to 444. In thiscase, these components are driven by the control unit on the basis ofthe measured values determined by the sensor element and on the basis ofthe predefined color value distribution of the multicolor volumehologram such that the exposure of the volume hologram master iseffected by light having different wavelengths or light having differentangles of incidence such that it is effected in register with thepredefined color values of the multicolor volume hologram. With the aidof the sensor element it is likewise possible to detect the position ofthe multilayer body 52 with the volume hologram layer 12, for example bymeans of optical register marks applied on the multilayer body 52, andthereby to drive the lasers 44 a, 44 b, 44 c and/or the modulators 441to 444 such that an exposure of the volume hologram master can beeffected with register accuracy or in register with design elementsalready present on the multilayer body 52.

FIG. 12 a illustrates the optical impression 80—which arises for anobserver—of one possible embodiment of a multicolor volume hologram,produced in accordance with FIG. 1 b or FIG. 1 c. The number “50” andthe characters “50 DOLLARS” appear red. The lines surrounding the “50”exhibit an optical effect of apparently moving morphing or cross-fadingfrom a green rectangle to a green star when the element is horizontallytilted/moved. The characters “USA” appear blue.

FIG. 12 b shows a volume hologram master 81 used for writing the volumehologram. The background is formed by black mirror structures or motheye structures (non-image-generating) and the design elements areproduced with diffractive structure types that are different therefrom.The morphing from a green rectangle to a green star is produced e.g. bythe same structures having a varying azimuth. The red and blue elements“50”, “50 DOLLARS” and “USA” can have a structure different therefrom,but jointly identical, including with the same azimuth, e.g. 0 degrees.The design elements have a distance 82, 83, which has to be greater thanthe necessary tolerance in the positioning of the laser beam on themaster.

FIG. 12 c shows the volume hologram master 81 and the regions of thevolume hologram master 81 which are irradiated by means of differentlycolored lasers. A first laser, which emits red light, at a first angleof incidence irradiates the regions 84, which produces red designelements. A second laser, which emits green light, irradiates the region86, which produces green design elements. A third laser, which emitsblue light, irradiates the regions 85, which produces blue designelements. The angles of incidence of the differently colored lasers canbe identical or different in each case. Instead of differently coloredlasers, in this example, too, it is also possible to use lasers havingthe same color, but with a different angle of incidence per region 84,85, 86 with respect to the surface of the volume hologram master 81.

Multicolored volume holograms can be produced in this way. In the caseof a volume hologram master 81 having a correspondingly fine gridstructure with closely adjoining domains (pixels) of different colors(e.g. RGB), it is also possible, by means of additive color mixing, toproduce true color holograms based on the color mixing of theintermeshing grids of the individual colors. For this purpose, thevolume hologram master 81 can have a homogeneous, uniform structurewhich is irradiated in each case with coherent light having differentcolors and/or at different angles of incidence. For this purpose,however the volume hologram master 81 can also have a homogeneous,uniform structure only in certain domains. Furthermore, in the exposurestation 40, the film body 52, after the writing of the volume hologram,is additionally exposed with UV light 46 from the side of the top sideof the multilayer body 52 in order at least partly to cure thephotopolymer of the volume hologram layer and to fix the Bragg planes ofthe volume hologram layer. This exposure is preferably effected using anon-collimated UV light source, such that a largest possible domain ofthe domains of the volume hologram layer 12 which are arranged below thepartial metallic layer 13 is cured by the irradiation. Exposure usingcollimated UV light is also possible.

The resultant multilayer body 53 is then fed to the exposure station 54,in which the multilayer body 53 is exposed with UV light from theunderside and the remaining, not fully cured domains of the volumehologram layer are thus fully cured as well.

FIG. 7 then illustrates the construction of a security element 62 whichhas been produced by the methods described above. The security element62 has the carrier layer 10, the replication layer 11, the partialmetallic layer 13, the volume hologram layer 12 and an adhesive layer14. In this case, the adhesive layer 14 can also be colored andpreferably has a dark pigment. Preferably, the adhesive layer 14 iscolored black in this case or a black interlayer is provided between thevolume hologram layer 12 and the adhesive layer 14. The adhesive layer14 can also be dispensed with or in addition or instead of the adhesivelayer 14, one or a plurality of further layers, for example a furthermetallic layer and/or a decorative layer, can also be provided. Thus, itis also possible, for example, for a decorative layer, for example colorlayer, shaped in pattern form to be applied to the volume hologram layerbefore the adhesive layer 14 is applied. In this case, the decorativelayer is preferably printed on by means of a printing method, forexample in the form of a logo or a pattern. The decorative layer canalso be applied before the application of the security element 62 onto asubstrate (not illustrated in more specific detail), preferably printedon by means of a printing method, for example offset printing,flexographic printing or screen printing, for example in the form of alogo or a pattern. The security element 62 can then be applied inparticular with register accuracy with respect to the decoration on thesubstrate.

In this case, the decoration can consist of conventional printing inks,but also of special security colors or security inks which contain, inparticular, special pigments that produce optically variable effects,for example Merck Iriodin effect pigments.

The metallic layer 13 is provided in the zones 31 of the securityelement 62 and not provided in the zones 32 of the security element 62.As shown in FIG. 7, the relief structure 21 is furthermore molded in thezones 31. In the domains 32, the relief structure is cancelled by thecoating with the material of the volume hologram layer or not actuallymolded into the replication layer 11 in the first place, as has beenexplained above. In the zones 32, a volume hologram is written into thevolume hologram layer, wherein the domains in which the Bragg planes ofthe volume hologram are formed in the volume hologram layer 12 arecorrespondingly identified in FIG. 7. In the zones 31, in this casedomains are provided in which no volume hologram is written into thevolume hologram layer 12, as has already been explained above. By meansof the relief structure 21 covered with the metallic layer 13, a firstoptically variable information item is provided in the domains 31. Inthe domains 32, instead of said first information item, a secondoptically variable information item different therefrom is provided bythe volume hologram written into the volume hologram layer 12 in thezones 32. In the zones 31 and 32, therefore, different optical effectsare generated, which are generated without a boundary domain directlyalongside one another, such that no superimposition phenomena thatdisturb or corrupt said effects occur in the boundary domains.Furthermore, it is possible for the zones 31 to be provided alternatelyand for first zones that succeed one another in at least one directionto be spaced apart from one another by less than 300 μm. Such anarrangement of the zones 31 and 32 is illustrated by way of example inFIG. 8.

FIG. 8 shows a schematic, greatly enlarged plan view of a domain of thesecurity element 62. In a domain 30 of the security element 62, thezones 31 and 32 are arranged in accordance with a regular,one-dimensional periodic grid. The width of the zones 31 is in the rangeof approximately 100 μm and the distance between successive zones 31 isapproximately 240 μm. The length of the zones 31 is chosen here suchthat the domain 30 having this arrangement of zones 31 and 32 is shapedin pattern form in the form of a cross. By virtue of such aconfiguration of the zones 31 and 32, an optically variable impressionresulting from the superimposition of the first and second opticallyvariable information items, for example a metallic cross 31 and a number32, arises for the human observer in the domain 30.

Diverse interesting optical effects can also be obtained by the zones 31and 32 not being arranged in accordance with a periodic grid.Preferably, the zones 31 in this case have a width of less than 300 μm,preferably a width of 150 to 50 μm, and are shaped in the form of thinlines having a length of >300 μm. These lines are furthermore shaped inthe form of complex patterns, for example in the form of a guilloche orfor representing a pictorial representation, for example a portrait.Furthermore, it is also possible for the first zones 31 to shape arepetitive pattern, for example in the form of a repeating number or arepeating logo.

In one embodiment variant, the replication layer has diffractivestructures arranged alongside one another, preferably completely orpartially metallized (or partially covered with other reflection layers)as described above, and valleys of a refractive, macroscopic structure,which are filled with the photopolymer material 37 and thereby form apartial volume hologram layer 12. If a multilayer body 52 constituted inthis way is exposed in the exposure station 40 by means of the laser 44with coherent light 45 and the volume hologram master 41 andsubsequently cured, the interference pattern of the volume hologramarises only in the domains in which the photopolymer material 37 ispresent in a layer thickness sufficient for this purpose. No volumehologram is produced in the other domains. As a result, it is possibleto combine domains having metallized reflection holograms which liealongside one another with register accuracy with domains having volumeholograms which are arranged adjacent thereto. Likewise, it is thuspossible for the partial domains which are filled with the photopolymermaterial 37 to be arranged as dots in a regular or irregular grid,wherein the grid is preferably so fine that it cannot be resolved by thehuman eye. By way of example, such a grid has a resolution of 300 dpi(dots per inch) or higher. It is only within these volume hologram dotsthat an interference pattern of the volume hologram is produced, andhence an optically variable effect. Outside the dots of the grid, adifferent optical effect or else no optical effect is visible ascontrast. Consequently, it is possible for the image informationcontained in the volume hologram master 41 to be reproduced only partlyin the volume hologram layer 12 or for the image information containedin the volume hologram master 41 to be superimposed with further imageinformation in the form of the shaping of the domains filled withphotopolymer material 37.

This will be explained below with reference to FIGS. 9 a to 11 b.

FIG. 9 a shows a film body 91 having the carrier layer 10 and thereplication layer 11, which are formed in the manner described abovewith reference to FIGS. 1 a to 8. In this case, a relief structure 22 ismolded into the replication layer 11, which relief structure has arelief depth of more than 10 μm, preferably between 20 and 50 μm, infirst regions 71 and has a relief depth of less than 1 μm, in thisexemplary embodiment a relief depth of 0, in second regions 72.

A photopolymer present in liquid form is then applied to the undersideof the film body 91 as volume hologram material—as described above forexample in the exemplary embodiments according to FIGS. 1 a to 8. Aphotopolymer corresponding to the photopolymer 37 described above can beused as volume hologram material. Preferably, the volume hologrammaterial is introduced into the depressions of the relief structure bymeans of a doctor blade, thus resulting in the film body shown in FIG. 9b, wherein the relief structure 22 is filled with the volume hologrammaterial in the regions 71. However, it is also possible to dispensewith introducing the volume hologram material by doctor blade if thevolume hologram material is chosen with a correspondingly low viscosity,such that the volume hologram material, after application, penetrates,in particular flows, into the depressions substantially independently.Furthermore, it is also possible for the volume hologram material to bepresent not only in the regions 71, but also in the regions 72, whereinit is essential here for the layer thickness of the volume hologramlayer thus present to be at least 10 μm thicker in the regions 71 thanin the regions 72.

Afterward, as described above with reference to FIGS. 1 a to 8, a volumehologram is written into the volume hologram layer 12 partially presentin the regions 71, and the volume hologram material of the volumehologram layer 12 is then cured and the volume hologram is thus fixed.With regard to the details of this part of the method, reference is madeto the explanations concerning FIGS. 1 a to 8, that is to say that thispart of the method is carried out in a manner corresponding to thatdescribed with reference to FIGS. 1 a to 8.

In the regions 71, the relief structure 22 preferably has a relief depthof between 10 and 50 μm, with further preference between 15 and 40 μm.The width of the regions 71, that is to say the smallest dimensionthereof, is preferably more than 20 μm. The regions 71 can be shaped inaccordance with the zones 32 according to FIG. 2 to FIG. 8. Furthermore,it is also possible for the zones 72 to be chosen such that theirsmallest dimension is less than 400 μm, preferably less than 200 μm andthat the area proportion constituted by the zones 71 in the domain ofthe volume hologram is varied in order in this way, in addition, for thebrightness of the volume hologram as it appears to the observeradditionally to be varied. In this case, it is possible, firstly, forthe regions 71 to be formed substantially uniformly, for example to havethe form of a point or of a polygon, and for the distance between theregions 71 to be varied locally, as a result of which a different areaoccupancy of the domains by the regions 71 arises in adjacent domains.Furthermore, it is also possible for the regions 71 to be arranged in aregular grid and for the regions 71 to vary in terms of their size, thatis to say for the area occupied by them to vary.

Furthermore, it is also possible for the regions 71 to be formed in theform of fine lines having a line width in the range of between 20 μm and400 μm, preferably 75 μm to 200 μm, particularly preferably between 30μm and 60 μm. By virtue of such a configuration of the regions 71 it ispossible to create a security element which can be counterfeited onlywith difficulty. Such a security element cannot be copied by means ofthe partial writing of a volume hologram, nor can it be obtained bymeans of printing methods, etc., on account of the customary propertiesof volume hologram material, with the result that an impressive securityfeature which can be counterfeited only with very great difficulty isprovided. Preferably, the fine lines in this case represent pictorialinformation, for example a portrait or a numeric code. It is furthermorealso advantageous to form the lines in the form of a security pattern,for example in the form of a guilloche or a Moiré pattern.

FIG. 10 a to FIG. 10 c illustrate the production of a further securityelement according to the invention.

FIG. 10 a shows a film body 93 having the carrier layer 10 and thereplication layer 11. A relief structure 23 is molded into thereplication layer 11.

The relief structure 23 differs from the relief structure 22 accordingto FIG. 9 a in that structure elements having a relief depth of lessthan 2 μm, in particular less than 1 μm, which are suitable forgenerating an optically variable effect, are molded in the regions 72.The relief structure in the regions 72 thus forms for example a reliefstructure formed like the relief structure 20 and/or 21 according toFIG. 2 to FIG. 8.

That surface of the replication layer 11 which is provided with therelief structure 23 is then provided with a metallic layer, the metallayer 13, in a portion of the regions 72 or in partial regions of theregions 72, which metal layer is thus present in zones 31 and is notpresent in zones 32, as already explained above with reference to FIGS.2 to 8.

This can be realized by the metal layer 13 being applied by means of avapor deposition mask only in the regions 72, or by the surface of therelief structure 23 being provided with a metallic layer over the wholearea and the metal layer then being removed again in the regions 71 andin the regions 72 in which the fine structure formed by the structureelements is not provided.

This can be effected for example by printing on an etchant/etchingresist.

This results in a film body 94 in which the metallic layer 13 is notprovided in the regions 71 and the metallic layer 13 is provided in allor a portion of the regions 72 or in partial regions of the regions 72.

Afterward, the volume hologram material is applied to the underside ofthe film body 94, that is to say that side of the film body 94 which isprovided with the partial metal layer, as already explained above withreference to FIG. 9 b, a volume hologram is written and the volumehologram material is crosslinked, thus resulting in the film body shownin FIG. 10 c. This film body exhibits the same optical appearance as,for example, the film body according to FIG. 7 a and FIG. 8 with thedifference that, in the zones 32, the luminous intensity of the volumehologram is additionally varied by the configuration of the regions 71,as explained above.

FIG. 10 d thus shows by way of example one possible optical appearanceof the film body 95, in which a volume hologram with varying luminousintensity in the form of a portrait is manifested in a zone 32 coatedwith photopolymer and a Kinegram® shaped in the form of the numbers“100” with contours is manifested in a zone 31 free of photopolymer,said zone being formed as gaps in the zone 32. By virtue of thestructures for forming the zones 31 and 32, said structures beingproduced with the same volume hologram master, the Kinegram® in the zone31 is arranged with register accuracy and, as shown in FIG. 10 d,closely adjacent and with uniform distance relative to the edge of thezone 32, which is difficult to counterfeit and results in a securityelement which is difficult to forge. In this case, as described above,the zone 32 with a volume hologram can consist of a grid of smallregions with photopolymer, that is to say of photopolymer appliedpartially in grid form, the local grid width producing the localbrightness value of the volume hologram. It is likewise possible for thezone 32 with a volume hologram to consist of photopolymer which isapplied over the whole area in said zone 32 and into which a motif isexposed.

A further possibility for producing a film body according to theinvention is explained below with reference to FIGS. 11 a and 11 b.

FIG. 11 a shows a film body 96 having the carrier layer 11 and thereplication layer 13. The film body 96 is constructed like the film body91 according to FIG. 9 a with the difference that, instead of the reliefstructure 22, a relief structure 24 is molded into the underside of thereplication layer 11 and all regions 72 are covered with the metalliclayer 13. The relief structure 24 is formed like the relief structure 23according to FIG. 10 a with the difference that all regions 72 areoccupied by structure elements which generate an optically variableinformation item. This is not mandatory, however. In this case, thefollowing methods are preferably used for producing the partial metallayer 13: the underside of the replication layer 13 with the reliefstructure 24 is coated with a metallic layer over the whole area, forexample by vapor deposition and sputtering. An etching resist issubsequently applied by means of a printing roller. On account of therelatively high difference in the relief depth between the regions 71and 72, the printing roller only wets the “elevated” regions 72 with theetching resist, such that the etching resist is applied to the regions72 with register accuracy without an additional measure. The metal layeris subsequently removed in the domain not protected by an etchingresist, in an etching process. Furthermore, it is also possible for therelatively large difference in the relief depth in the regions 71 and 72to be utilized to the effect that an etchant is applied and introducedby doctor blade into the regions 71, such that the metal layer isremoved by the etchant in the regions 71, but not in the regions 72.

FIGS. 10 b, 10 c and 11 a, 11 b in each case illustrate the case inwhich the relief structure 23, 24 is completely covered with the metallayer 13. It is likewise possible for the metal layer 13 to only partlycover the relief structure 23, 24, for example in the form of an aerialgrid or as a partial metal layer 13 in register with a molded design inthe relief structure 23, 24.

Afterward, the film body 96, as explained above in accordance with FIG.9 b, is coated with a volume hologram material, a volume hologram iswritten into the volume hologram layer thus formed, and the volumehologram material is then cured and the volume hologram is thus fixed.This results in the film body 97. As already noted above, it is notnecessary in this case for the volume hologram layer 12 not to bepresent in the regions 72. As shown in FIG. 11 b, it suffices if thevolume hologram layer 12 has a layer thickness of preferably less than 5μm in the regions 72.

The invention claimed is:
 1. A security element in the form of amultilayered film body having a top side facing the observer, whereinthe security element has a volume hologram layer, in which a volumehologram is recorded, which provides a first optically variableinformation item, wherein the security element has a replication layer,in the surface of which a relief structure providing a second opticallyvariable information item is molded and which is arranged above thevolume hologram layer, and wherein a partial metallic layer is arrangedbetween the volume hologram layer and the replication layer, wherein themetallic layer is provided in one or a plurality of first zones of thesecurity element and the metallic layer is not provided in one or aplurality of second zones of the security element, and the volumehologram is written in the volume hologram layer through the partialmetallic layer functioning as an exposure mask.
 2. The security elementas claimed in claim 1, wherein the relief structure is molded into theunderside of the replication layer, wherein, in the first zones a firstsurface of the metallic layer adjoins the replication layer and a secondsurface of the metallic layer, lying opposite the first surface, adjoinsthe volume hologram layer, and wherein, in the second zones, thereplication layer adjoins the volume hologram layer.
 3. The securityelement as claimed in claim 1, wherein the difference in refractiveindex between the material of the replication layer and the materialprovided at the top side of the volume hologram layer is less than 0.2.4. The security element as claimed in claim 1, wherein the material andthe layer thickness of the metallic layer are chosen such that thedegree of opacity of the metallic layer is greater than 80%.
 5. Thesecurity element as claimed in claim 1, wherein the one or the pluralityof first or second zones are shaped in pattern form for the purpose offorming a third information item.
 6. The security element as claimed inclaim 1, wherein first and second zones are provided alternately in afirst domain of the security element, wherein first zones succeeding oneanother in at least one direction are spaced apart from one another byless than 300 μm.
 7. The security element as claimed in claim 6, whereinthe ratio of the average width of the first zones to the ratio of theaverage width of the second zones in the first domain is between 0.75:1and 1:5.
 8. The security element as claimed in claim 6, wherein thefirst and second zones are arranged in accordance with a regular, one-or two-dimensional grid.
 9. The security element as claimed in claim 6,wherein the first domain has a smallest dimension of more than 300 μmand is shaped in pattern form for the purpose of forming a fourthinformation item.
 10. The security element as claimed in claim 1,wherein two or more information items from the group of first, second,third and fourth information items represent mutually completelyinformation items.
 11. The security element as claimed in claim 1,wherein the relief structure is molded into the replication layer onlyin the first zones, but not in the second zones.
 12. The securityelement as claimed in claim 1, wherein the volume hologram is recordedin the volume hologram layer in the first zones, but not in the secondzones.
 13. The security element as claimed in claim 1, wherein thevolume hologram is not recorded in the volume hologram layer in at leastone partial domain of each of the second zones.
 14. The security elementas claimed in claim 13, wherein the volume hologram is not recorded inthe volume hologram layer at least in 90%, of the area of the secondzones.
 15. A method for producing a security element in the form of amultilayered film body having a top side facing the observer, wherein amultilayer body comprising a partial metallic layer and a replicationlayer is provided, wherein a relief structure providing a secondoptically variable information item is molded in a surface of thereplication layer and the metallic layer is provided in one or aplurality of first zones of the security element and the metallic layeris not provided in one or a plurality of second zones of the securityelement, wherein a volume hologram layer is applied on that surface ofthe multilayer film body which lies closer to the metallic layer than tothe replication layer, such that the partial metallic layer is arrangedbetween the volume hologram layer and the replication layer, and whereinthe volume hologram layer is exposed with coherent light from that sideof the multilayer body which faces away from the volume hologram layer,through the partial metallic layer for the purpose of recording a volumehologram in the volume hologram layer.
 16. The method as claimed inclaim 15, wherein a volume hologram master is arranged below the volumehologram layer during the exposure.
 17. The method as claimed in claim15, wherein during the exposure, the multilayer body is guided via aroller, in the lateral surface of which a surface relief forming avolume hologram master is molded.
 18. The method as claimed in claim 15,wherein the exposure of the volume hologram master is effected by meansof two or more lasers, whereby a multicolored volume hologram isrecorded as volume hologram into the volume hologram layer.
 19. Themethod as claimed in claim 18, wherein the light beams generated by thetwo or more lasers impinge on the volume hologram layer at differentangles of incidence.
 20. The method as claimed in claim 18, wherein thetwo or more lasers generate light having different wavelengths.
 21. Themethod as claimed in claim 18, wherein the light generated by the two ormore lasers is coupled by means of a coupler in a light beam used toexpose the volume hologram layer.
 22. The method as claimed in claim 18,wherein each of the two or more lasers is assigned an exposure mask or amodulator, which is arranged in the beam path between the respectivelaser and the volume hologram layer.
 23. The method as claimed in claim18, wherein the two or more lasers and/or the modulators are controlledby a control device, which detects the position of the volume hologrammaster by means of a sensor element and, by means of the informationthus determined about the relative position of the volume hologrammaster with respect to the two or more lasers, drives the lasers and/orthe modulators for the purpose of recording the multicolor volumehologram.